The present invention relates to a total intervertebral joint prosthesis, i.e. a prosthesis for both the disc and facets.
The degeneration of an intervertebral disc is commonly treated by implanting an intervertebral disc prosthesis. Such a prosthesis nevertheless has the drawback of not treating the facet joints, which may also have deteriorated due to the repeated non-physiological movements of the vertebrae resulting from the degeneration of the disc.
Inappropriate implantation of an intervertebral disc prosthesis may also be a source of degeneration of the facet joints.
In order to resolve this problem, total vertebral joint prostheses have been designed, i.e. comprising prosthetic disc joint portions rigidly connected, by connecting arms, to prosthetic facet joint portions, cf. in particular patent application publication No. WO 2005/067824 A1. The disc joint and the facet joints are thus precisely positioned relative to one another, which allows precise control of the interactions of the disc joint with the facet joints.
Such a known combined prosthesis comprises two pairs of elongated elements designed for posterior implementation, one pair being designed to be placed in the intervertebral space on the left side of the vertebral bodies of the two considered vertebrae, and the other pair being designed to be placed in the intervertebral space on the right side of those vertebral bodies; each element of a pair of elements comprises a disc joint surface, a facet joint surface, and a connecting arm extending between said disc joint surface and said facet joint surface; when the two elements of a same pair of elements are placed one above the other, the disc joint surface of one element cooperates with the disc joint surface of the other element, and the facet joint surface of one element cooperates with the facet joint surface of the other element.
It nevertheless appears that the existing combined prostheses are not optimal. In fact, these prostheses can cause a risk of imperfect restoration of the physiological movement of the vertebrae, and, in particular, of being capable of undergoing significant wear over time. Certain prostheses include means for positioning one pair of elements relative to the other, which does not, however, exclude more or less significant imprecision in the positioning of one pair of elements relative to the other. Several other prostheses are purely and simply provided without means for positioning one pair of elements relative to the other. Furthermore, the existing combined prostheses have relatively complex and costly structures to manufacture.